The present disclosure relates to coding techniques for multi-directional imaging applications.
Some modern imaging applications capture image data from multiple directions about a camera. Some cameras pivot during image capture, which allows a camera to capture image data across an angular sweep that expands the camera's effective field of view. Some other cameras have multiple imaging systems that capture image data in several different fields of view. In either case, an aggregate image may be created that merges image data captured from these multiple views.
A variety of rendering applications are available for multi-directional content. One rending application involves extraction and display of a sub-set of the content contained in a multi-directional image. For example, a viewer may employ a head mounted display and change the orientation of the display to identify a portion of the multi-directional image in which the viewer is interested. Alternatively, a viewer may employ a stationary display and identify a portion of the multi-directional image in which the viewer is interested through user interface controls. In these rendering applications, a display device extracts a portion of image content from the multi-directional image (called a “viewport” for convenience) and displays it. The display device would not display other portions of the multi-directional image that are outside an area occupied by the viewport.
In such applications, therefore, a display device receives image data that exceeds the data that is needed to be displayed. When received data is coded by video compression techniques, a decoding device may be employed to decode compressed image data of the multi-directional image in its entirety before presenting the multi-directional image to the display for rendering. Decoding such image data involves processing latencies that can delay rendering of viewport data.
Accordingly, the inventors perceive a need in the art for video coding techniques that code data of multi-directional images but avoid unnecessary latencies in generating viewport data for display applications.